SPEED
OF SOUND
In our
This Week in History section we talked
about how the sound barrier was broken this week when a rocket plane
flew faster than the speed of sound. Now let's explore a bit more about
the speed of sound. Sound travels at different speeds depending upon
exactly what it is traveling through. For example, sound can travel
through gases, liquids, or solids. Gases, liquids, and solids are referred
to as mediums. The temperature of these mediums can also affect the
speed of sound.
When sound
is traveling through a gas, like the air we breathe, the temperature
of the gas is very important. At lower temperatures, sound waves can
move faster. At freezing temperature, which is 0 degrees Celsius, sound
travels through air at a speed of 331 meters per second (about 740 miles
per hour). When the temperature of air is 20 degrees Celsius, sound
will travel at a faster speed of 343 meters per second (767 miles per
hour).
Sound will
travel faster in liquids than it will in gases. In fresh water, sound
waves will travel at 1,482 meters per second (about 3,315 miles per
hour). This speed is over four times faster than the speed of sound
in the air! Many ocean animals rely on sound waves to talk with other
animals and to locate food. One reason that these animals are able to
do this so well over long distances in the water is because sound travels
so fast in water!
Generally,
sound will travel the fastest in solids! The molecules that make up
a solid are so much closer together than the molecules that make up
a liquid or a gas and this fact allows sound to travel very, very quickly
through a solid. Sound will actually travel over 17 times faster through
steel than through air! The exact speed of sound through steel is 5,960
meters per second (13,332 miles per hour)! Not all solids allow sound
to travel this quick, but steel is a very fast example.
MEXICO
FLOODING
We discussed
the terrible floods that hit Mexico in this week's paper. Here is some
more information about Mexico. Mexico is part of North America. It is
located just south of the United States of America beneath the states
of Texas, Arizona, California, and Oklahoma. Mexico has a vast culture.
It has first class tourist resorts and big cities, snow-capped volcanoes
and pine forests, and deserts and beaches.
Mexico
is very large. It covers almost two million square kilometers (800,000
square miles) and curves from northwest to southeast. The Pacific Ocean
borders the west coast of Mexico and the Gulf of Mexico borders the
east coast. The population of Mexico is 96 million people! Most Mexicans
are of Hispanic and Native American background. The northern part of
Mexico is not very crowded, but Mexico City is becoming one of the world's
most populated cities.
Coffee,
grown mainly in the Gulf Coast of Mexico is Mexico's most valuable export
crop. An export crop is a crop that Mexico will sell to other countries.
Other products also grown in Mexico are sugar, vanilla, and cotton.
Mexico's
climate changes quite a bit throughout the year. The hot and wet season
is May to October. Then from October to May is a more pleasant time.
Hidalgo,
Tabasco, and Villahermosa are three places that we reported were really
affected by recent flooding. Villahermosa and Tobasco are located in
the southeastern part of Mexico and Hidalgo is located in the northeast
part of the country bordering the USA.
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